New Install - Erratic Overnight Charging

[lper]

Evening all. First time contributor, long time lurker
I had a new solar system installed at the beginning of September (details below). Thus far, really happy. I'm already seeing savings in excess of my expectations. However, over the last few nights I've noticed a very erratic charge rate when charging my SolaX battery from the grid. I generally set a two hour charge window to correspond to the Octopus Agile tariff when it's cheapest. Up until a few days ago I was waking up to a full battery going from 10% to 100% in the two hour charge window.

From around the 7th of November the battery stopped getting to 100% and only achieved numbers like 51% 62% from my two hour charge window. Looking at the charge history for these periods the battery is only achieving a charge rate of 10amps for the first hour or so and then gradually rising to around 19amps toward the end of the charge and only occasionally hitting 25+amps.

As an aside I have "boosted" the charge when I realised that it wasn't fully charged and and have achieved 25amps almost from the get go at 7am! Hence going from 50% to 100% in a little over an hour

My question is this:-

Am I being unrealistic to expect the battery (5.8kWh) to charge from 10%-100% in two hours (Even though it has done frequently in the past. What would the normal charge time be?
What could be the cause of this low charging rate?

I have been in contact with Solax technical support who have tried to brush me aside by telling me that this is due to the UK getting colder recently and that will affect the battery performance. By that token I'll be proper stuffed when it gets really cold! I think that theory is a bit out there considering the temperature here in Mid Wales has not changed dramatically over the last few days. Happy to be corrected though if that really is the case.

Many thanks in advance for you thoughts.
Warm regards

Leigh

12 x 435w Longi Solar Panels
SolaX X1 Hybrid 5.0kW Inverter
SolaX Triple Power 5.8Kwh Master Battery

 

[EcoBob]

Hi Iper,
I have a Solax X3 hybrid 15kW + 3 x T58 batteries, located in our barn. Like you, my battery charging current has dropped dramatically since early October. In summer, the current went straight up to about 30A and stayed there, so 2 hours for a full charge. It has recently dropped to as low as 7A for a couple of hours before slowly ramping up, so an 80% charge has been taking up to 4 hours (the battery starting temp for the charge was 15 - 16C).

Looking at the SolaxCloud app on a phone (not the pc version) you can see the battery temperature profile and sure enough, as the temp has dropped, so has the charge current. In fact, you can see that as the charge current warms the batteries, this allows the current to rise.

As a result, I insulated all around my batteries with 40mm PIR insulation sheet, leaving a small airgap to allow air to circulate and this raised the temp by 4-5 degrees, increasing the current noticeably. I've now added a couple of ebay sourced 45W 28x80cm vivarium heaters in underneath (the batteries are hung on the wall) Even with the system turned off for 24 hours, on switch on, the batteries reported a temp of 25 degrees C, so I think I can turn them down a bit. Just waiting now for the first overnight charge to see if things are better

 

[SeaGal]

I have been in contact with Solax technical support who have tried to brush me aside by telling me that this is due to the UK getting colder recently and that will affect the battery performance.

They are technically correct. However, the installers should have made sure that the batteries were installed in a location that remains above 15C for charge rates to remain normally high. So get them back to recify.

Otherwise, if they have been installed in an outbuilding or loft you will need to add heater & insulation as @EcoBob has done. There are many threads on doing similar on here from last Winter! e.g, quite a lot of details incl pics in this thread from my posting here onwards...

Solis RHI 6K 48ES 5G Inverter Fox ESS LV5200 Battery - Charging limit ? and export to grid ...

I'm thinking - based on the seeming randomness - that it is temperature related and the FOX ESS has got a faulty temp measurement. - i.e. it thinks it's colder than it is. Is it warmer and sunnier where you are today? Call FOX again if they haven't got back yet.

diysolarforum.com

also here...

Solis RAI not charging Fox-ESS LV5200 correctly

Hi all, hoping someone can shed some light on this. My Solis RAI charger is programmed to charge the battery from the grid for 4 hours every night on cheap-rate electricity, but it is not getting much of a charge. Software I have on the computer shows 640W going out to the workshop, where the...

diysolarforum.com

As a result, I insulated all around my batteries with 40mm PIR insulation sheet, leaving a small airgap to allow air to circulate and this raised the temp by 4-5 degrees, increasing the current noticeably. I've now added a couple of ebay sourced 45W 28x80cm vivarium heaters in underneath (the batteries are hung on the wall) Even with the system turned off for 24 hours, on switch on, the batteries reported a temp of 25 degrees C, so I think I can turn them down a bit.

My DIY 14.3kWh battery uses 20W heater on about 50% of time in unheated garage, with 50mm PIR surrounding it.
Saturday am; garage temp -1C; LiFePO4's 22.6C

 

[EcoBob]

The results from my heating experiment are in.
Without heating on 3/12/23: Charging start temp 16C, start current 7.5A, end current 21A, end temp 22C, 4 hours 10-90%
With heating on 5/12/23 Charging start temp 25C, start current 29A, end current 30A, end temp 37C 1hr 30 mins 10-90%

Temps as reported by the inverter stats. Looks like I now need to sort out a thermostat and set an optimum ambient temp. Don't want to fry the cells when the weather is warmer.

 

[SeaGal]

Looks like I now need to sort out a thermostat and set an optimum ambient temp. Don't want to fry the cells when the weather is warmer.

Yep. 45W is a lot of heat if on all the time. I use 20W, thermostically controlled and it's only on 30% to 50% of the time, with the 50% being when it was -1 in the garage last week.

25C is optimum for the cells and too hot is not good either, so if you can aim for 15C to 30C, then IMHO that's a good range to target. Mine generally keep from 18 to 27-ish, with the heater thermostat set to come on at 18 and off at 21C - the peaks being during overnight charge up on economy 7.